I actually reached out to their support because the autoplaying (sound on) playlist previews on the music tab caught me off-guard. I asked how to disable the sound on them and got this as a response.
> We've checked this further and it sounds indeed like you’re seeing a recent change to the app we’ve made for some users. We’re always testing possible improvements, so you or someone else may see something new or get a limited feature temporarily.
> We understand you have some feedback about the auto previews so we suggest sharing your thoughts on our Community page: https://community.spotify.com/. In the meantime, we can recommend keeping your phone with the silent mode on and making sure your phone's sound volume is also reduced to zero.
> We've checked this further and it sounds indeed like you’re seeing a recent change to the app we’ve made for some users. We’re always testing possible improvements, so you or someone else may see something new or get a limited feature temporarily.
> We understand you have some feedback about the auto previews so we suggest sharing your thoughts on our Community page: https://community.spotify.com/. In the meantime, we can recommend keeping your phone with the silent mode on and making sure your phone's sound volume is also reduced to zero.